NJM13600D equal to LM137000?

[RaceDriver205]

Whats the deal with the NJM13600D from small bear? At that price id use them instead of lm13700 for everything!
Has anyone used it interchangeably with the lm13700?
Cheers, R205

[Paul Perry (Frostwave)]

In many circuits (including all the FX ones I can think of) it makes no difference.
The crucial difference, according to Scott Stites is this:

"The LM13700 has the Darlington buffer unbiased, where in the LM13600,
the darlington is biased by the Iabc current.
The gain cell between the two is identical. Therefore, if you are not using the buffers, there would be no discernible difference between the two.
There are a few cases where one device may work fine, but the other not so fine. One case I recall is the original MS-20 filter (the later version that used the LM13600 OTA instead of the custom Korg IC) - JH noted on the Synth DIY list that replacing the LM13600 with an LM13700 did not work out too well - there was more thumping with the LM13700.
But, as mentioned before, if you're not using the Darlington buffer, there's nothing to worry about, and I imagine in most applications, even when using the buffer, one probably wouldn't notice much difference, except, perhaps in some cases, on fast transients. "

Matches my experience.

[R.G.]

Yeah - this is a subtle point. The darlington in the LM13700 is biased, but it's a constant bias, not tied to Iabc. National Semi notes that there will be differences in performance. They say that the performance of the LM13700 may be superior for audio applications. I have found differences in thumping, but I've found it both ways.

Paul's advice is right on - if you don't use the darlington buffer, it doesn't matter; and in either case, fast changes in the Iabc are the place where it would show up.

[cjlectronics]

To apply what RG and Paul have stated, I repaired a Ross Phaser (USA) where all of the opamps were replaced with LM13700.  The phaser was weak and didn't have much life to it.  Per the schematic, all of the IC's are LM13600.  I replaced the IC's with the LM13600 and the pedal came alive.  Obviously, the circuit was designed around the 13600.  I didn't pursue investigating this any further but I sure noted it in my repair log.